Scholarly Work - Earth Sciences

Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/8747

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Reconciling petrologic magma ascent speedometers for the June 12th, 1991 eruption of Mt. Pinatubo, Philippines
(Volcanica, 2024-03) Harris, Megan; Hosseini, Behnaz; Myers, Madison; Bouley, Logan
We investigate whether decompression rates derived from three often-disparate petrologic techniques (microlites, bubbles, and melt embayments) can be reconciled or integrated for a more complete understanding of magma ascent in the conduit. We focus on the well-studied and -documented earliest Plinian eruptions (June 12, 1991) of Mount Pinatubo. Using a newly developed two-stage decompression-diffusion model, volatile profiles in quartz-hosted embayments reveal an initial stage of decompression nearly two orders of magnitude slower than final rates. In applying time-integrated models of microlite and bubble nucleation and growth, initial decompression rates from embayments are supported by microlite modeling results, whereas final rates are in close agreement with bubble number densities. This consistency and continuity between speedometers supports the sensitivity of different petrologic recorders to specific regions of the conduit system and highlights the fidelity of embayments as recorders of decompression throughout the entire conduit. Ascent timescales derived from Pinatubo embayments range from hours to days, coinciding with the visual onset of lava effusion leading to explosive activity.
Wood–Ljungdahl pathway encoding anaerobes facilitate low-cost primary production in hypersaline sediments at Great Salt Lake, Utah
(Oxford University Press, 2024-07) Shoemaker, Anna; Maritan, Andrew; Cosar, Su; Nupp, Sylvia; Menchaca, Ana; Jackson, Thomas; Dang, Aria; Baxter, Bonnie K.; Colman, Daniel R.; Dunham, Eric C.; Boyd, Eric S.
Little is known of primary production in dark hypersaline ecosystems despite the prevalence of such environments on Earth today and throughout its geologic history. Here, we generated and analyzed metagenome-assembled genomes (MAGs) organized as operational taxonomic units (OTUs) from three depth intervals along a 30-cm sediment core from the north arm of Great Salt Lake, Utah. The sediments and associated porewaters were saturated with NaCl, exhibited redox gradients with depth, and harbored nitrogen-depleted organic carbon. Metabolic predictions of MAGs representing 36 total OTUs recovered from the core indicated that communities transitioned from aerobic and heterotrophic at the surface to anaerobic and autotrophic at depth. Dark CO2 fixation was detected in sediments and the primary mode of autotrophy was predicted to be via the Wood–Ljungdahl pathway. This included novel hydrogenotrophic acetogens affiliated with the bacterial class Candidatus Bipolaricaulia. Minor populations were dependent on the Calvin cycle and the reverse tricarboxylic acid cycle, including in a novel Thermoplasmatota MAG. These results are interpreted to reflect the favorability of and selectability for populations that operate the lowest energy requiring CO2-fixation pathway known, the Wood–Ljungdahl pathway, in anoxic and hypersaline conditions that together impart a higher energy demand on cells.
Evaluating Cosmic Ray Neutron Sensor Estimates of Snow Water Equivalent in a Prairie Environment Using UAV Lidar
(American Geophysical Union, 2024-06) Woodley, M.; Kim, H.; Sproles, E.; Eberly, J.; Tuttle, S.
Monitoring snow cover in prairie environments is important for understanding water and energy fluxes, agricultural production, and flooding, but difficult due to shallow snowpack and considerable snow heterogeneity. Cosmic ray neutron sensors (CRNS) are sensitive to snow within a radius of 150–250 m, which allows for continuous estimation of snow water equivalent (SWE) over a large footprint and may better represent area-averaged snow cover in prairies than conventional SWE instruments, such as snow pillows. A CRNS was installed at Montana State University's Central Agricultural Research Center (CARC; 47.06°, −109.95°) in Moccasin, MT in coordination with NASA's SnowEx 2021 field campaign. This work assesses the feasibility of a CRNS for SWE monitoring in prairies by comparing CRNS SWE estimates to spatially distributed SWE derived from uninhabited aerial vehicle lidar snow depths within the sensor's footprint and manual snow pit measurements. Lidar observations show snow cover was highly spatially variable, with the largest snow accumulation near barriers and the least in barren fields. Additionally, we evaluate our CRNS SWE estimates using Ultra Rapid Neutron Only Simulation (URANOS) Monte Carlo simulations. Comparisons of SWE estimates derived from lidar, CRNS, and URANOS for shallow snowpack at the site yielded root mean square values of about 2 mm (approximately 30% of the mean SWE). These results suggest that the CRNS is effective at integrating over significant spatial variability within its footprint at this site. However, the spatial distribution of snow exerts a strong influence on the CRNS signal and must be considered when interpreting CRNS observations.
Travertine records climate-induced transformations of the Yellowstone hydrothermal system from the late Pleistocene to the present
(Geological Society of America, 2024-02) Harrison, Lauren N.; Hurwitz, Shaul; Paces, James B.; Whitlock, Cathy; Peek, Sara; Licciardi, Joseph
Chemical changes in hot springs, as recorded by thermal waters and their deposits, provide a window into the evolution of the postglacial hydrothermal system of the Yellowstone Plateau Volcanic Field. Today, most hydrothermal travertine forms to the north and south of the ca. 631 ka Yellowstone caldera where groundwater flow through subsurface sedimentary rocks leads to calcite saturation at hot springs. In contrast, low-Ca rhyolites dominate the subsurface within the Yellowstone caldera, resulting in thermal waters that rarely deposit travertine. We investigated the timing and origin of five small travertine deposits in the Upper and Lower Geyser Basins to understand the conditions that allowed for travertine deposition. New 230Th-U dating, oxygen (δ18O), carbon (δ13C), and strontium (87Sr/86Sr) isotopic ratios, and elemental concentrations indicate that travertine deposits within the Yellowstone caldera formed during three main episodes that correspond broadly with known periods of wet climate: 13.9−13.6 ka, 12.2−9.5 ka, and 5.2−2.9 ka. Travertine deposition occurred in response to the influx of large volumes of cold meteoric water, which increased the rate of chemical weathering of surficial sediments and recharge into the hydrothermal system. The small volume of intracaldera travertine does not support a massive postglacial surge of CO2 within the Yellowstone caldera, nor was magmatic CO2 the catalyst for postglacial travertine deposition.
Growth rate affects blood flow rate to the tibia of the dinosaur Maiasaura
(Cambridge University Press, 2023-09) Seymour, Roger S.; Caldwell, Heath R.; Woodward, Holly N.; Hu, Qiaohui
Fossil bones were once living tissues that demanded internal blood perfusion in proportion to their metabolic requirements. Metabolic rates were primarily associated with bone growth (modeling) in the juvenile stages and with alteration and repair of existing bone affected by weight bearing and locomotion (remodeling) in later stages. This study estimates blood flow rates to the tibia shafts of the Late Cretaceous hadrosaurid Maiasaura peeblesorum, based on the size of the primary nutrient foramina in fossil bones. Foramen size quantitatively reflects arterial size and hence blood flow rate. The results showed that the bone metabolic intensity of juveniles (ca. 1 year old) was greater than fourfold higher than that of 6- to 11-year-old adults. This difference is much greater than expected from standard metabolic scaling and is interpreted as a shift from the high metabolic demands for primary bone modeling in the rapidly growing juveniles to a lower metabolic demand of adults to remodel their bones for repair of microfractures accumulated during locomotion and weight bearing. Large nutrient foramina of adults indicate a high level of cursorial locomotion characteristic of tachymetabolic endotherms. The practical value of these results is that juvenile and adult stages should be treated separately in interspecific analyses of bone perfusion in relation to body mass.
A framework to link climate change, food security, and migration: unpacking the agricultural pathway
(Springer Science and Business Media LLC, 2024-03) Tuholske, Cascade; Di Landro, Maria Agustina; Anderson, Weston; van Duijne, Robbin Jan; de Sherbinin, Alex
Researchers have long hypothesized linkages between climate change, food security, and migration in low- and middle-income countries (LMICs). One such hypothesis is the “agricultural pathway,” which postulates that negative climate change impacts on food production harm livelihoods, which triggers rural out-migration, internally or abroad. Migration is thus an adaptation to cope with the impacts of climate change and bolster livelihoods. Recent evidence suggests that the agriculture pathway is a plausible mechanism to explain climate-related migration. But direct causal connections from climate impacts on food production to livelihood loss to rural out-migration have yet to be fully established. To guide future research on the climate-food-migration nexus, we present a conceptual framework that outlines the components and linkages underpinning the agricultural pathway in LMICs. We build on established environmental-migration conceptual frameworks that have informed empirical research and deepened our understanding of complex human-environmental systems. First, we provide an overview of the conceptual framework and its connection to the agricultural pathway hypothesis in the climate mobility literature. We then outline the primary components and linkages of the conceptual framework as they pertain to LMIC contexts, highlighting current research gaps and challenges relating to the agricultural pathway. Last, we discuss possible future research directions for the climate-food-migration nexus. By highlighting the complex, multiscale, interconnected linkages that underpin the agricultural pathway, our framework unpacks the multiple causal connections that currently lie hidden in the agricultural pathway hypothesis.
Hazardous heat exposure among incarcerated people in the United States
(Springer Science and Business Media LLC, 2024-03) Tuholske, Cascade; Lynch, Victoria D.; Spriggs, Raenita; Ahn, Yoonjung; Raymond, Colin; Nigra, Anne E.; Parks, Robbie M.
Climate change is predicted to increase the frequency of potentially hazardous heat conditions across the United States, putting the incarcerated population of 2 million at risk for heat-related health conditions. We evaluate the exposure to potentially hazardous heat for 4,078 continental US carceral facilities during 1982–2020. Results show that the number of hot days per year increased during 1982–2020 for 1,739 carceral facilities, primarily located in the southern United States. State-run carceral facilities in Texas and Florida accounted for 52% of total exposure, despite holding 12% of all incarcerated people. This highlights the urgency for enhanced infrastructure, health system interventions and treatment of incarcerated people, especially under climate change.
The coevolution of rostral keratin and tooth distribution in dinosaurs
(The Royal Society, 2024-01) Aguilar-Pedrayes, Isaura; Gardner, Jacob D.; Organ, Chris L.
Teeth evolved early in vertebrate evolution, and their morphology reflects important specializations in diet and ecology among species. The toothless jaws (edentulism) in extant birds likely coevolved with beak keratin, which functionally replaced teeth. However, extinct dinosaurs lost teeth multiple times independently and exhibited great variation in toothrow distribution and rhamphotheca-like keratin structures. Here, we use rostral jawbone surface texture as a proxy for rostral keratin covering and phylogenetic comparative models to test for the influence of rostral keratin on toothrow distribution in Mesozoic dinosaurs. We find that the evolution of rostral keratin covering explains partial toothrow reduction but not jaw toothlessness. Toothrow reduction preceded the evolution of rostral keratin cover in theropods. Non-theropod dinosaurs evolved continuous toothrows despite evolving rostral keratin covers (e.g. some ornithischians and sauropodomorphs). We also show that rostral keratin covers did not significantly increase the evolutionary rate of tooth loss, which further delineates the antagonistic relationship between these structures. Our results suggest that the evolution of rostral keratin had a limited effect on suppressing tooth development. Independent changes in jaw development may have facilitated further tooth loss. Furthermore, the evolution of strong chemical digestion, a gizzard, and a dietary shift to omnivory or herbivory likely alleviated selective pressures for tooth development.
Origin of CO2 in Upper Devonian Duperow Formation and the Bakken Petroleum System at Kevin Dome, Northwest Montana
(Elsevier BV, 2023-11) Adeniyi, E.O.; Tyne, R.L.; Barry, P.H.; Darrah, T.H.; Hubbard, M.S.; Myers, M.L.; Shaw, C.A.; Bowen, D.W.; Calavan, C.W.
Carbon capture and storage (CCS) is a key mitigation strategy in achieving global net-zero emissions. It is therefore essential to identify and characterize potential subsurface storage repositories. Natural CO2 accumulations provide an opportunity to understand the behavior of CO2 in the subsurface. Here, we investigate the source(s), migration, and storage of CO2 in the Upper Devonian Duperow Formation at Kevin Dome, northwest Montana, USA within the Bakken Petroleum System. We report, major gas, stable and noble gas isotopic compositions in bulk gas samples (n = 19) produced from nearby hydrocarbon-bearing reservoirs at Kevin Dome and compare with CO2 bearing fluid inclusions (n = 24) from the Duperow Formation. Using the same methods, bulk gas samples (n = 9) from the adjacent Ferguson Field, (Exshaw/Bakken Petroleum System) in southern Alberta, Canada, and fluid inclusions from the Sweetgrass Hills igneous complex (n = 2) were analyzed to understand CO2 generation and the subsequent processes affecting CO2 regionally. We find that CO2 in the Upper Devonian Duperow Formation is magmatic in origin, likely related to the nearby Sweetgrass Hills igneous complex intrusion (∼52 Ma), whereas CH4 and N2 gases are generated predominantly by thermogenic processes associated with hydrocarbon generation during burial. Since emplacement, most CO2 in the hydrocarbon-bearing reservoirs of the Bakken petroleum system at Kevin Dome (∼98%) and the Ferguson Field (∼82%) has subsequently been dissolved into the groundwater. We employ a solubility model to calculate minimum gas/water ratios in Kevin Dome and the Ferguson Field, which are consistent with more groundwater interaction and more dissolution at Kevin Dome. Understanding the subsurface processes affecting CO2 is critical for future CO2 storage site selection.
The patchwork governance of ecologically available water: A case study in the Upper Missouri Headwaters, Montana, United States
(Wiley, 2023-09) Cravens, Amanda E.; Goolsby, Julia B.; Jedd, Theresa; Bathke, Deborah J.; Crausbay, Shelley; Cooper, Ashley E.; Dunham, Jason; Haigh, Tonya; Hall, Kimberly R.; Hayes, Michael J.; McEvoy, Jamie; Nelson, Rebecca L.; Poděbradská, Markéta; Ramirez, Aaron; Wickham, Elliot; Zoanni, Dionne
Institutional authority and responsibility for allocating water to ecosystems (“ecologically available water” [EAW]) is spread across local, state, and federal agencies, which operate under a range of statutes, mandates, and planning processes. We use a case study of the Upper Missouri Headwaters Basin in southwestern Montana, United States, to illustrate this fragmented institutional landscape. Our goals are to (a) describe the patchwork of agencies and institutional actors whose intersecting authorities and actions influence the EAW in the study basin; (b) describe the range of governance mechanisms these agencies use, including laws, policies, administrative programs, and planning processes; and (c) assess the extent to which the collective governance regime creates gaps in responsibility. We find the water governance regime includes a range of nested mechanisms that in various ways facilitate or hinder the governance of EAW. We conclude the current multilevel governance regime leaves certain aspects of EAW unaddressed and does not adequately account for the interconnections between water in different parts of the ecosystem, creating integrative gaps. We suggest that more intentional and robust coordination could provide a means to address these gaps.
Increased whitebark pine (Pinus albicaulis) growth and defense under a warmer and regionally drier climate
(Frontiers Media SA, 2023-03) Kichas, Nickolas E.; Pederson, Gregory T.; Hood, Sharon M.; Everett, Richard G.; McWethy, David B.
Introduction: Tree defense characteristics play a crucial role in modulating conifer bark beetle interactions, and there is a growing body of literature investigating factors mediating tree growth and resin-based defenses in conifers. A subset of studies have looked at relationships between tree growth, resin duct morphology and climate; however, these studies are almost exclusively from lower elevation, moisture-limited systems. The relationship between resin ducts and climate in higher-elevation, energy-limited ecosystems is currently poorly understood. Methods: In this study, we: (1) evaluated the relationship between biological trends in tree growth, resin duct anatomy, and climatic variability and (2) determined if tree growth and resin duct morphology of whitebark pine, a high-elevation conifer of management concern, is constrained by climate and/or regional drought conditions. Results: We found that high-elevation whitebark pine trees growing in an energy-limited system experienced increased growth and defense under warmer and regionally drier conditions, with climate variables explaining a substantive proportion of variation (∼20–31%) in tree diameter growth and resin duct anatomy. Discussion: Our results suggest that whitebark pine growth and defense was historically limited by short growing seasons in high elevation environments; however, this relationship may change in the future with prolonged warming conditions.
Episodic Late Cretaceous to Neogene crustal thickness variation in southern Tibet
(Wiley, 2023-10) Sundell, Kurt E.; Laskowski, Andrew K.; Howlett, Caden; Kapp, Paul; Ducea, Mihai; Chapman, James B.; Ding, Lin
Recent advancements in quantitatively estimating the thickness of Earth's crust in the geologic past provide an opportunity to test hypotheses explaining the tectonic evolution of southern Tibet. Outstanding debate on southern Tibet's Cenozoic geological evolution is complicated by poorly understood Mesozoic tectonics. We present new U-Pb geochronology and trace element chemistry of detrital zircon from modern rivers draining the Gangdese Mountains in southern Tibet. Results are similar to recently published quantitative estimates of crustal thickness derived from intermediate-composition whole rock records and show ~30 km of crustal thinning from 90 to 70 Ma followed by thickening to near-modern values from 70 to 40 Ma. These results extend evidence of Late Cretaceous north–south extension along strike to the west by ~200 km, and support a tectonic model in which an east–west striking back-arc basin formed along Eurasia's southern margin during slab rollback, prior to terminal collision of India with Eurasia.
Kilometer-scale recumbent folding, tectonic attenuation, and rotational shear in the western Anaconda Range, southwestern Montana, USA
(Geological Society of America, 2023-10) Neal, Bryce A.; Laskowski, Andrew K.; Lonn, Jeffrey D.; Burrell, William B.
The Eocene Anaconda metamorphic core complex is the most recently documented metamorphic core complex in the North American Cordillera. While much work has focused on constraining the nature and timing of core complex extension, earlier deformation preserved in its footwall is not as well understood. The Anaconda metamorphic core complex footwall contains an anomalously thin, lower- to uppermost-amphibolite-facies section of Mesoproterozoic Belt Supergroup and Paleozoic metasedimentary strata. While the tectonic nature of this thinning is generally accepted, the mechanisms behind it remain enigmatic. Previous workers have hypothesized that footwall strata were attenuated along the upper limb of the Late Cretaceous Fishtrap recumbent anticline, a kilometer-scale, NW-vergent, recumbent fold exposed throughout the west-central metamorphic core complex footwall. New geologic mapping in the west-central Anaconda Range better constrains the nature and timing of tectonic attenuation in this structurally complex area. Two generations of folds were recognized: (1) F1 recumbent isoclines associated with the Fishtrap recumbent anticline and (2) F2 W-vergent asymmetric folds associated with map-scale N-plunging folds. F1 folds, axial planar S1 transposition fabrics, and bedding-parallel faults and shear zones boudinage, transpose, and omit strata of the Belt Supergroup. We suggest that the Fishtrap recumbent anticline tectonically attenuated the Belt Supergroup through Paleozoic section of the west-central Anaconda metamorphic core complex footwall, and we propose that it is a kilometer-scale, regionally significant structure. We further propose that the fold may have developed in response to rotational shear and sinistral transpression along the Lewis and Clark Line, which was further driven by accretion of outboard terranes along the western margin of North America during Late Cretaceous time.
Assessment of L-band InSAR snow estimation techniques over a shallow, heterogeneous prairie snowpack
(Elsevier BV, 2023-10) Palomaki, Ross T.; Sproles, Eric A
Snow water equivalent (SWE) is a critical input for weather, climate, and water resource management models at local to global scales. Despite its importance, global SWE measurements that are accurate, consistent, and at sufficiently high spatiotemporal resolutions are not currently available. L-band interferometric synthetic aperture radar (InSAR) techniques have been used to measure SWE at local to regional scales, and two upcoming L-band SAR satellite missions have renewed interest in these techniques to provide regular SWE measurements at the global scale. However, previous research demonstrating the capabilities of L-band InSAR-SWE measurement has been limited to mountain or tundra snowpack regimes. Here we examine the feasibility of applying the same techniques over a prairie snowpack, which are typically characterized by shallow snow depths (mean snow depth of 0.22 m in this study), exposed agricultural vegetation, and high spatial variability over short distances. Our study area in central Montana, USA (47.060, -109.951) was a validation site for NASA SnowEx 2021, as part of the UAVSAR snow timeseries. Airborne L-band SAR imagery was acquired by the UAVSAR platform while concurrent snow measurements were collected using uncrewed aerial vehicle (UAV)-based LiDAR, UAV-based photogrammetry, and ground-based manual techniques. This validation dataset enables an investigation of the effects of sub-pixel snow cover heterogeneity and exposed agricultural vegetation stubble on SAR data and the resulting SWE estimations. Results based on repeated application of the Kolmogorov–Smirnov test show that UAVSAR VV phase change is sensitive to differences in snow cover but relatively unaffected by differences in agricultural stubble height. However, we did not find similarly definitive results when we used the same phase change data to estimate SWE. Although broad spatial patterns were similar in both LiDAR-derived and InSAR-derived SWE estimates, considerable differences in the two estimates were apparent in areas with large sub-pixel snow depth variability. Our results indicate that additional work is necessary to derive accurate SWE estimates in prairie environments. Regular measurements from L-band SAR satellites will provide an excellent opportunity to refine InSAR-based snow estimation techniques over shallow, heterogeneous snowpacks.
Tree-Ring Derived Avalanche Frequency and Climate Associations in a High-Latitude, Maritime Climate
(Wiley, 2023-07) Peitzsch, E. H.; Hood, E.; Harley, J. R.; Stahle, D. K.; Kichas, N. E.; Wolken, G. J.
Snow avalanches are a natural hazard in mountainous areas worldwide with severe impacts that include fatalities, damage to infrastructure, disruption to commerce, and landscape disturbance. Understanding long-term avalanche frequency patterns, and associated climate and weather influences, improves our understanding of how climate change may affect avalanche activity. We used dendrochronological techniques to evaluate the historical frequency of large magnitude avalanches (LMAs) in the high-latitude climate of southeast Alaska, United States. We collected 434 cross sections throughout six avalanche paths near Juneau, Alaska. This resulted in 2706 identified avalanche growth disturbances between 1720 and 2018, which allowed us to reconstruct 82 years with LMA activity across three sub-regions. By combining this tree-ring-derived avalanche data set with a suite of climate and atmospheric variables and applying a generalized linear model to fit a binomial regression, we found that February and March precipitation and the Oceanic Niño Index (ONI) were significant predictors of LMA activity in the study area. Specifically, LMA activity occurred during winters with substantial February and March precipitation and neutral or negative (cold) ONI values, while years not characterized by LMAs occur more frequently during warm winters (positive ONI values). Our examination of the climate-avalanche relationship in southeast Alaska sheds light on important climate variables and physical processes associated with LMA years. These results can be used to inform long-term infrastructure planning and avalanche mitigation operations in an urban area, such as Juneau, where critical infrastructure is subject to substantial avalanche hazard.
The egg-thief architect: experimental oviraptorosaur nesting physiology, the possibility of adult-mediated incubation, and the feasibility of indirect contact incubation
(Cambridge University Press, 2023-08) Hogan, Jason D.
Numerous, high-quality reproduction-related oviraptorosaur fossils have been described. However, oviraptorosaur-style nests are unknown among extant animals, and their curious construction makes nesting behavior difficult to interpret. Experiments were undertaken to better understand oviraptorosaur nesting strategies. A surrogate was constructed and placed atop mock-oviraptorosaur nests built from sand and 36 infertile emu eggs (as Macroolithus approximations) arranged according to the most current nest reconstructions. Thermometers, placed within each egg and throughout the experimental area, recorded energy flow from the surrogate dinosaur into the nesting microenvironment. One experiment examined a basic open nest warmed from above; the second, a fully buried clutch warmed from above; and the third, a nest open like the first but with heating elements (representing hindlimbs) extending down into the nest. It was found that egg temperatures in each scenario surpassed ambient temperatures without requiring excessive energy input. Final clutch temperatures were below most avian values, closer to crocodilian incubation, but are likely conservative, considering experimental parameters. These results may support the idea that an oviraptorosaur could use adult-generated energy to warm a clutch above ambient conditions. Additionally, egg tiers would be warmer and more uniform in temperature if heated by elements within the nest, such as hindlimbs, instead of solely from above. Results from the second experiment indicate that an endothermic adult could possibly warm a clutch fully buried beneath itself despite a barrier. Although not likely a behavior exhibited by oviraptorosaurs, such results suggest an important evolutionary step bridging guarded subterranean eggs and contact-incubated subaerial eggs.
Chthonic severance: dinosaur eggs of the Mesozoic, the significance of partially buried eggs and contact incubation precursors
(The Royal Society, 2023-07) Hogan, Jason D.; Varricchio, David J.
For most dinosaurs, clutches consisted of a single layer of spherical to sub-spherical, highly porous eggs that were probably fully buried. Both eggs and clutch form change drastically with pennaraptoran theropods, the clade that includes birds. Here, far less porous, more elongate eggs are arranged with additional complexity, and only partially buried. While partial egg burial seems to be effective for an extremely small group of modern birds, the behaviour's overall rarity complicates our understanding of Mesozoic analogies. Recent experimental examination of pennaraptoran nesting thermodynamics suggests that partial egg burial, combined with contact incubation, may be more efficacious than has been presumed. We propose that nest guarding behaviour by endothermic archosaurs may have led to an indirect form of contact incubation using metabolic energy to affect temperature change in a buried clutch through a barrier of sediment, which in turn may have selected for shallower clutch burial to increasingly benefit from adult-generated energy until partial egg exposure. Once partially exposed, continued selection pressure may have aided a transition to fully subaerial eggs. This hypothesis connects the presence of partially buried dinosaurian clutches with the transition from basal, crocodile-like nesting (buried clutches guarded by adults) to the dominant avian habit of contact incubating fully exposed eggs.
Public Water System Governance in Rural Montana, USA: A ‘Slow drip’ on Community Resilience
(Informa UK Limited, 2023-05) Gansauer, Grete; Haggerty, Julia; Dunn, Jennifer
Recent waves of U.S. federal waterworks investments aim to repair material as well as socioeconomic deficits. Yet a growing recognition of the central role of local capacity in successful water resources and infrastructure governance raises questions about the extent to which such investments will engender more resilient rural communities. Synthesizing resilience theory with the drinking water governance literature, we use qualitative methods to assess the social, economic, and environmental dimensions of public water system governance in a case study of six small towns in an agricultural region. We find that shortfalls in local social and economic capital constrain localities from adapting to environmental vulnerabilities, and that the current policy environment exacerbates—rather than ameliorates—tradeoffs between community capitals. In addition to funding increases for rural infrastructure deficits, this study implies that process reform in water quality compliance and financial assistance program delivery will also be needed to bolster rural community resilience.
Using High‐Resolution Satellite Imagery and Deep Learning to Track Dynamic Seasonality in Small Water Bodies
(American Geophysical Union, 2023-04) Mullen, Andrew L.; Watts, Jennifer D.; Rogers, Brendan M.; Carroll, Mark L.; Elder, Clayton D.; Noomah, Jonas; Williams, Zachary; Caraballo‐Vega, Jordan A.; Bredder, Allison; Rickenbaugh, Eliza; Levenson, Eric; Cooley, Sarah W.; Hung, Jacqueline K. Y.; Fiske, Greg; Potter, Stefano; Yang, Yili; Miller, Charles E.; Natali, Susan M.; Douglas, Thomas A.; Kyzivat, Ethan D.
Small water bodies (i.e., ponds; <0.01 km2) play an important role in Earth System processes, including carbon cycling and emissions of methane. Detection and monitoring of ponds using satellite imagery has been extremely difficult and many water maps are biased toward lakes (>0.01 km2). We leverage high-resolution (3 m) optical satellite imagery from Planet Labs and deep learning methods to map seasonal changes in pond and lake areal extent across four regions in Alaska. Our water maps indicate that changes in open water extent over the snow-free season are especially pronounced in ponds. To investigate potential impacts of seasonal changes in pond area on carbon emissions, we provide a case study of open water methane emission budgets using the new water maps. Our approach has widespread applications for water resources, habitat and land cover change assessments, wildlife management, risk assessments, and other biogeochemical modeling efforts.
Are We Recording? Putting Embayment Speedometry to the Test Using High Pressure‐Temperature Decompression Experiments
(American Geophysical Union, 2023-06) Hosseini, Behnaz; Myers, Madison L.; Watkins, James M.; Harris, Megan A.
Despite its increasing application to estimate magma decompression rates for explosive eruptions, the embayment speedometer has long awaited critical experimental evaluation. We present the first experimental results on the fidelity of natural quartz-hosted embayments in rhyolitic systems as recorders of magma decompression. We conducted two high pressure-temperature isobaric equilibrium experiments and 13 constant-rate, continuous isothermal decompression experiments in a cold-seal pressure vessel where we imposed rates from 0.005 to 0.05 MPa s−1 in both H2O-saturated and mixed-volatile (H2O + CO2)-saturated systems. In both equilibrium experiments, we successfully re-equilibrated embayment melt to new fluid compositions at 780°C and 150 MPa, confirming the ability of embayments to respond to and record changing environmental conditions. Of the 32 glassy embayments recovered, seven met the criteria previously established for successful geospeedometry and were thus analyzed for their volatile (H2O ± CO2) concentrations, with each producing a good model fit and recovering close to the imposed decompression rate. In one H2O-saturated experiment, modeling H2O concentration gradients in embayments from three separate crystals resulted in best-fit decompression rates ranging from 0.012 to 0.021 MPa s−1, in close agreement with the imposed rate (0.015 MPa s−1) and attesting to the reproducibility of the technique. For mixed-volatile experiments, we found that a slightly variable starting fluid composition (2.4–3.5 wt.% H2O at 150 MPa) resulted in good fits to both H2O + CO2 profiles. Overall our experiments provide confidence that the embayment is a robust recorder of constant-rate, continuous decompression, with the model successfully extracting experimental conditions from profiles representing nearly an order of magnitude variation (0.008–0.05 MPa s−1) in decompression rate.

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